The Synthesis And Modification Of Zeolitic Precursor PLS-4

Zeolites are widely utilized in industrial catalysis, because of their unique property of pore structure. However, there is still a fundamental demand for new zeolitic framework as well as innovative applications. Recently, layered zeolitic precursors are research focus, because of framework modification.In this thesis, a novel synthetic route to layered material PLS-4is described which uses self-made high-active silica as a silica source and self-made ethyldimethylethanolammonium fluoride as a organic structure-directing agent. The reactions take place under high reactants concentrations and utilize fluoride delivered as the quaternary ammonium fluoride salt rather than as ammonium fluoride or hydrofluoric acid. Introducing aluminum, alkali metals and alkaline earth metals into the aforementioned system, we obtained PLS-4with four different morphologies. Thus far, it’s first time to report directing-synthesis of Al-PLS-4zeolitic precursor. Then, we modified the PLS-4with dimethyldiethoxysilane under acidic condition and obtained COE-4zeolite.Layered zeolitic precursor PLS-4and zeolite COE-4are characterized by X-ray diffusion, scanning electron microscope, solid-state nuclear magnetic resonance and nitrogen adsorption etc. We have successfully synthesized PLS-4with three new morphologies (blade-plate, large single crystal and flower-like) by introducing aluminum, alkali metals and alkaline earth metals. The results indicate that the silylation reaction only increase the pore diameter and specific surface of products and keep the morphology unchanged.